Jump to content
SAU Community

Recommended Posts

hey guys iv'e been rebuilding a rb25 from the ground up, i put the bottom end back up, with CP forged pistons and rb26 conrods (which my brother got :unsure: ) i had it all spinning, THEN i put the head on, tightened it down (stupid thing to do) then spinning the crank, and it seems its locked in place??? doesnt turn clockwise/anti-clockwise??? its STUCK ?! i double checked that the valves wern't hitting pistons, they wern't. So i only have 2 other feasible options. either;

1. Iv'e tightened the con-rod bolts to tight, but this cant be because iv'e spun the engine before hand.

2. The head hasn't been machined to fit the new 87mm CP pistons, which is causing a sort of lip between the block and the head, so the piston cannot move.

Does anyone have any helpful ideas, i need a solution urgently, as this is for my year 12 automotive HSC and i need the engine complete ASAP! :(

Link to comment
https://www.sau.com.au/forums/topic/362563-rb25det-not-turning-over/
Share on other sites

yes cams are in the motor, i made sure valves aren't touching by checking which pistons are at the top, and then checked where the lobes are on the cams to make sure none of the valves were pushed down, i have CYL 1 at BTDC and the cams at 15 degree mark where they are mean't to be, and their is no timing belt

If there is no cam belt, then the cams won't turn with the crank, and you will end up with valves still protruding into piston space.

What does "CYL 1 at BTDC" mean? Do you mean TDC? (B = Before)

How does the RB26 rod compare in length to RB25 rods? Maybe the RB26 rods are too long, and are trying to push the piston crown into the combustion chamber.

thanks for that info mad082, really appreciate, im thinking of taking the head off instead of the cams, as its alot easier, BTDC, it just before top dead centre, where i its mean't to sit, or its top dead centre. im still learning mechanics, so bear with me please! :) the engine has no movement Clockwise OR Anti-Clockwise, like the pistons are superglued to the cylinder wall lol...

yes, but if you just take out the cams you can confirm it is pistons touching valves which is the most likely. Just undo the cam bolts slowly, start at the middle and undo a turn or 2 at a time on each bolt.

also, are the spark plugs in? if so when you try and turn the balancer it is producing compression which can make it harder than you expect to turn the motor. But either way I would not turn it far before putting the timing belt on.

You mentioned #1 is at TDC which is correct. The pin in the cams should point at the marking on the backing plate, or about 280o on lnlet and 70o on exhaust.

But if it was the valves hitting, i would atleast be able to move it the other way, like clockwise would make piston go up a little more and hit valve, but if i go anti-clockwise, it would just go back down not going near the valves, and no their is no sparkplugs. thanks alot for the info :)

But if it was the valves hitting, i would atleast be able to move it the other way, like clockwise would make piston go up a little more and hit valve, but if i go anti-clockwise, it would just go back down not going near the valves, and no their is no sparkplugs. thanks alot for the info :)

not really. you have pistons going up and pistons going down at the same time. so the valves may be hitting 2 pistons stopping you from turning it either way.

but regardless, you shouldn't be trying to spin the engine without the cams turning as well otherwise you run the risk of damaging both pistons and valves

hey again, got some new updates; i took the head off today and it wasnt the problem, the engine is still locked in place, so me and the teacher tomorow are going to turn the engine over and have a look at the bottom end to see anything wrong,if their is nothing wrong their we are going to take off the oil pump, is it possible for the oil pump to cease up?

i would appreciate any information you would give,thanks

yeah i took apart the oil pump,the bolts were TIGHT AS :down: it fell apart in the 3 pieces but it's stuffed, it doesnt turn at all, so im going to buy a brand new oil pump or good 2nd hand one. It was the same one as i took off when i was rebuilding it...oh well, atleast we found the problem,and it was nothing serious like pistons hitting valves etc.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Didnt realise RB's had more then 1 head.
    • I'm normally copping my own abuse from neglecting my daily drivers. "Those suspension bushes will last a bit more", "Don't worry about the oil leak, just keep topping it up". The project cars I'm always doing things slowly on them as I'm wanting them to be done better, and neater, and nicer. Luckily I don't have to deal with 18 year old Matt's "Learning to wire" stuff in the project cars. And there's only one piece of wiring I'm displeased about in the Landcruiser, and it's about to be cut out... However, the box loads of parts that have been going through this place lately for the Landcruiser... Brake pads Brake Rotors Full handbrake overhaul Wheel Bearings Seals Swivel hubs Steering Boxes Half the suspension joints Shocks Air bags (Ones to go in the rear springs for towing) Water pump Timing kit Lower timing case Harmonic Balancer Radiator Lots of other little seals and shits Gas struts for the bonnet New power window switches And god knows what else I've forgotten... Ha ha ha I have my fingers crossed the pinion seals don't start leaking on the diffs, that the transfer case doesn't leak, and the gearbox input shaft doesn't leak, nor the rear main seal. As they're about the only seals I haven't replaced in the driveline! I'm seriously eyeing off buying new caliper rebuild kits front and rear brake calipers... I'll probably recheck all the valve clearances soon too, and hopefully, it should be all good and sweet to haul some long distance trips again!
    • Every time I pull my 3x gauges out of the console and see the crack-addict way that I did the wiring, and I just can't bring myself to tear it all apart and "make it nice", because it is currently working. In fact, the last time I was in there I probably made it worse.
    • The best part is when you own the car long enough that you look back and find your OWN ham fisted amateur shit!
    • The annoying part about neglect, is when you start to replace one thing, and find ten more broken things. Ham fisted monkey repairs you normally only find out about when trying to do something unrelated! Ha ha   Neglect you can kind of anticipate the huge costs to fix it all. Ham fistedness is normally a shock the first time your work on a new old car, as everything "looked" good before.
×
×
  • Create New...